What are the steel production?
By:Yvonne Aug 10, 2020
Steelmaking technology mainly has BF/BOF, EAF and DRI/EAF
Types of steel production
Steel production involves numerous process steps that can be laid out in various combinations depending on product mix, available raw materials, energy supply and investment capital. Key characteristics of the three main processing routes are as following:
◆ In Blast Furnace (BF)/Basic Oxygen Furnace (BOF) route, pig iron is produced using primarily iron ore (70-100%) and coke in a blast furnace, and then turned into steel in a basic oxygen furnace. Due to the inclusion of coke making and sintering operations, this route is highly energy intensive.
◆ Scrap/Electric Arc Furnace (EAF) route is primarily based on scrap for the iron input and has significantly lower energy intensity compared to the BF/BOF route due to the omission of coke making and iron making processes;
◆ Direct Reduced Iron (DRI)/EAF route, based on iron ore and often scrap for the iron input. Energy intensity of DRI production can be lower than BF route, depending on the size, and fuel and ore characteristics.
More types of steelmaking:
Sumitomo Top and Bottom Blowing process, developed by Sumitomo Metal Co., LTD in Japan. This method combines the advantages of oxygen top - blown bOF and oxygen bottom - blown Bof. Used for blowing low carbon steel, dephosphorization effect is good and cost reduction is significant. The bottom blowing gas used is O2, CO2, N2, etc. On the basis of STB method, STB - P method was developed to spray powder from the top, which further improved the dephosphorization condition of high carbon steel and was used to refine stainless steel.
Also known as cyclic vacuum treatment. It is jointly developed by Ruhrstahl/Heraeus from Germany. Two catheters are installed below the vacuum chamber, and the molten steel is inserted. After vacuuming, the molten steel rises to a certain height, and then the inert gas Ar is blown into the rising tube. Ar rises to drive the molten steel into the vacuum chamber for vacuum treatment, and then flows back to the ladle through another catheter. A feeding system with alloy in a vacuum chamber. This method has become the main vacuum treatment method for large capacity ladle (> 80t).
• RH - OB:
RH oxygen blowing. Heating is done by adding Oxygen Blowing in the vacuum cycle Degassing (RH) method. For refining stainless steel, it can be decarburized under reduced pressure. When used for refining ordinary steel, the load on the converter can be reduced. Aluminum heating can also be used.
• OBM -- S:
Oxygen Bottom Maxhutte -- Scarp, invented by Germany Maxhutte Klockner plant, using natural gas or propane-as the cooling medium of Oxygen gun, Oxygen Bottom blown converter steelmaking process. OBM - S is to install side blowing oxygen gun on the furnace cap of OBM oxygen bottom blowing converter. The bottom blowing oxygen gun blows gas and natural gas to preheat scrap steel, so as to increase scrap ratio.
• NK - CB:
NKK Combined Blowing System, established by Japan Steel Pipe Corporation in 1973, is used to blow a small amount of gas (Ar, CO2, N2) from the bottom of the bOF in order to strengthen the stirring of the slag and control the CO partial pressure in the molten steel. This method USES porous brick nozzle to make low carbon steel, which can reduce the cost. High carbon steel is beneficial to dephosphorization. This method should be combined with hot metal pretreatment.
A water-cooled oxygen gun is added to the equipment of VAD method to make it blow oxygen decarburization under vacuum. Since decarburization under vacuum is an exothermic reaction, vacuum heating measures of VAD method can be eliminated. The operation process is the same as VOD method.
Ladle Furnace refining method developed by Japanese Special Steel Corporation (Datong Special Steel Corporation) in 1971. The equipment and process are composed of argon gas mixing, submerged arc heating and alloy feeding system. The advantages of this process are that the chemical composition and temperature of the steel can be precisely controlled. Reduce inclusion content; High yield of alloying elements. LF furnace has become an indispensable refining equipment between steel furnace and continuous casting machine.
• LD steelmaking:
In 1952, Linz plant and Donawitz plant of Austrian Alps Mining and metallurgy company were the first to develop the successful oxygen top-blown converter steelmaking process in industry, and were named after the first letter of the two plants. The law was quickly spread around the world after it came into being. In the United States, it is called BOF or BOP method, short for Basic Oxygen Furnace or Process. See oxygen top blow converter.
• LD - OTB:
LD -- Oxgyen Top an Bottom Process, a Top - Bottom composite converter steelmaking Process developed by Kobe Steel Company and Furukawa Steel Plant in Japan. It is characterized by the use of a special bottom blowing single annular slot nozzle (SA nozzle), so that the bottom blowing gas can be controlled in a wide range. The bottom is blown with inert gas.
• LD - HC:
The original text is LD -- Hainaut Saubre CRM, a top and bottom composite converter steelmaking method developed in Belgium for the blowing of high phosphorus hot metal, namely LD+ bottom blowing oxygen with hydrocarbon protecting nozzle.
• LD - AC:
Ld-arbed-centre National, a top-blown oxygen spray lime powder steelmaking process developed by The French Iron and Steel Research Institute, is used for the smelting of high phosphorus iron water.
The Klockner Steelmaking process is a 100% solid material operation with pulverized coal injection and oxygen converter at the bottom. The bottom blowing oxygen ratio is 60% ~ 100%.
• K - ES:
The electric arc furnace process, a combination of bottom gas blowing, secondary combustion and pulverized coal injection, was developed by Tokyo Steelmaking Co. and Germany's Kiokner Corp. to generate electricity from coal.
• FINKL - VAD:
Arc heating ladle degassing or vacuum arc degassing. It is characterized by the addition of an arc heating device on the cover of the vacuum chamber and the use of argon gas in vacuum. The degassing effect of this method is stable, and it can desulphurize, decarbonize and add a lot of alloy. The equipment mainly consists of vacuum chamber, arc heating system, alloy feeding device, vacuum pumping system and hydraulic system.
A vacuum treatment device developed in association with Metallurgical Company, Dortmund Horder, Germany. The vacuum chamber lined with refractory material is inserted into the ladle with a refractory lined pipe at the bottom. The vacuum chamber or ladle is lowered and lifted periodically to make part of the molten steel enter the vacuum chamber and return to the ladle after treatment. The upper part adds the alloy material device and the vacuum heating insulation device. Such equipment is no longer being built.
A method for refining stainless steel. The principle is the same as AOD method, and water vapor is used instead of argon. The method was developed by Creusot-Loire in France and Uddeholm in Sweden, and was officially put into production in 1973. After contact with liquid steel, water vapor is decomposed into H2 and O2. H2 reduces the partial pressure of CO. At the same time, the decomposition reaction is endothermic, so the temperature rise of molten steel can be restrained. But the oxidation and burning loss of chromium is more serious than AOD method.
Composition Adjustment by sealed Argonbubbling, an out-of-furnace refining method of fine-tuning the alloy Composition under argon seal. In this method, argon is blown from the bottom of ladle. After the slag is removed, the dip cover is lowered, argon is continued to be blown, and then alloy fine-tuning is added. Its advantages are precise control of composition and high yield of alloy.
• CAS - OB:
The Compositon Adjustment by sealed argon bubbling with oxygen Blowing, is an out-of-furnace refining method of adding oxygen blowing guns to CAS equipment. In addition to reducing the fine tuning alloy composition, it can also add aluminum and blow oxygen temperature (chemical thermal method), the temperature rise rate is 5 ~ 13℃/ min. This method can control the temperature of molten steel accurately at ±3℃, which is beneficial to the continuous casting production.
• ASEA - SKF:
A ladle refining method developed in Sweden. It adopts low-frequency electromagnetic stirring, arc-heating under atmospheric pressure, slag refining in ladle, vacuum degassing in another station, and oxygen gun, which can blow oxygen and decarbonize under reduced pressure. In order to improve the refining effect, it can also blow argon stirring through porous brick at the bottom of ladle and add alloy to adjust the composition of molten steel.
Argon Oxygen Decarburisation and abbreviated as argon-Oxygen Decarburisation, is the main refining method for the smelting of low-carbon stainless steel. It was developed by American Carbide Company in 1964 and put into production in 1968. Its metallurgical principle is to dilute CO with Ar to reduce its partial pressure and achieve the effect of vacuum, thus making carbon decarburization to a very low level. The AOD furnace body and transmission device are similar to the converter. The air eye is placed on the side wall close to the bottom of the furnace, and Ar+O2 mixed gas is blown into the furnace. The raw material is molten steel from the primary smelting furnace. The blowing process is divided into oxidation period, reduction period and refining period. It has become the main production process of stainless steel.